Description

The erlport Python library implements Erlang external term format and Erlang port protocol for easier integration of Python and Erlang.

The library exports the following classes and functions:

• Port(packet=1, use_stdio=False, compressed=False) - class implementing port which connects with the corresponding Erlang port. See open_port/2 for description of packet and use_stdio arguments. compressed is the zlib compression level or True for the default of 6.

• Protocol() - class which simplifies creation of request-response protocols.

• Atom(str) - class which represents an Erlang atom.

• String(unicode | list) - class representing an Erlang string. Must be used as a wrapper if Unicode string expected instead of a list.

• BitBinary(str) - class representing an Erlang bitstring whose length in bits is not a multiple of 8.

• decode(str) - function to convert binary data into a term.

• encode(term, compressed=False) - function to convert a term into the external format. compressed is the zlib compression level or True for the default of 6.

• IncompleteData - exception raised by decode() in case of incomplete input data.

Installation

Prerequisites:

• Erlang >= R11B-4

• Python >= 2.4

To install the library use easy_install from setuptools package like this:

$ easy_install erlport

Examples

See examples directory in the source distribution for additional examples.

For simple request-response protocol use Port and Protocol on the Python side like this:

from erlport import Port, Protocol

class HelloProtocol(Protocol):

    def handle_hello(self, name):
        return "Hello, %s" % name

if __name__ == "__main__":
    proto = HelloProtocol()
    proto.run(Port(use_stdio=True))

On the Erlang side function hello() can be called like this:

-module(hello).
-export([hello/1]).

hello(Name) ->
    Port = open_port({spawn, "python -u hello.py"}, [{packet, 1}, binary]),
    port_command(Port, term_to_binary({hello, Name})),
    receive
        {Port, {data, Data}} ->
            binary_to_term(Data)
    end.

Test it in the Erlang shell:

1> c(hello).
{ok,hello}
2> hello:hello("Bob").
"Hello, Bob"

Notes for Windows users

• It seems Erlang’s open_port function ignores nouse_stdio option on Windows. So the Port class must be instantiated with use_stdio=True argument.

• Python must be ran with -u option to open stdin/stdout in binary mode.

Feedback

Please report bugs, offer suggestions or feedback at:

• Report bugs at http://github.com/hdima/erlport/issues

• Email me at <dima at hlabs.org>

• Write or follow me at http://twitter.com/hdima